Preparation And Properties Of High Strength Polyimide/Graphene Oxide Composite Nanofibers

Aromatic polyimides?PIs?,as a class of high-performance polymers,contain rigid imide heterocyclic rings and aromatic benzene rings in the macromolecular skeleton,exhibiting good thermal properties,chemical resistance and excellent properties.PIs are widely used in high temperature filtration,electronics,defense military,protective clothing,aerospace and automotive industries.Especially in recent years,PI electrospun nanofibers have exhibited fascinating and unique properties,such as large specific surface area,high porosity,and excellent mechanical properties.However,with the development of society,more and more high-performance polyimide fiber need to be prepared,particularly these possessing excellent mechanical properties.In order to improve the mechanical properties of electrospun PI nanofibers and their composites,Firstly,single electrospun PI/GO composite nanofiber with single layer of graphene oxide as inorganic filler was sucessfully prepared by in-situ polymerization and electrospinning.Secondly,the aligned electrospun PI/GO composite nanofiber belts were fabricated by the same method,and then obtain PI/GO composite nanofiber belts with different draw ratios were obtained via the hot drawing process.Finally,the aligned electrospun PI/GO composite nanofiber belts was used as a filler to enhance the soluble polyimide?SPI?.The structure and properties of different samples were studied and characterized.The specific research contents are as follows:1.Single electrospun PI/GO composite nanofiber was prepared by in-situ polymerization and electrospinning with single layer of GO as inorganic filler.The morphology,mechanical properties and thermal properties of electrospun PI/GO composite nanofibers were studied and characterized.The effects of different GO contents on the properties of electrospun PI/GO composite nanofiber were investigated.The results show that GO effectively improves the mechanical properties of single electrospun PI/GO composite nanofiber,the highest tensile strength and modulus are 3.92±0.26 GPa and 107.445±6.29 GPa,which are 42.5%and 251.5%higher than neat PI,respectively.In addition,electrospun PI/GO composite nanofibers exhibited good thermal properties.When the GO content was 1.2%,the electrospun PI/GO-1.2%composite nanofibers had the Tg of 299.6°C,the T_5%of 551.07°C and the residual of 61.51%at 800°C.2.The aligned electrospun PI/GO composite nanofiber belts with a GO content of 1.0%was prepared by the same experimental method in the previous chapter.The aligned electrospun composite nanofiber belts were further subjected to hot drawing process.And the effects of different draw ratios on the morphology,mechanical properties and thermal properties of the aligned electrospun composite nanofiber belts were investigated.The results show,when the draft ratio?=1.10,the performance of the aligned electrospun PI/GO-1.10 composite nanofiber belts is optimized,and the tensile strength and modulus are 1805.97±75.83 MPa and 38.15±2.52 GPa,which are increased by 39.1%and 140.5%,respectively,compared with the aligned PI/GO composite nanofiber belts.Moreover,a series of electrospun oriented PI/GO composite nanofiber belts prepared have excellent thermal properties,the T_10%thereof was above 564°C,and the residual ratio at 800°C was 61%or more.3.SPI was used as the matrix material,and the aligned electrospun PI/GO composite nanofiber belts with 1.0%GO content was used as the reinforcing filler.A series of composite films were prepared by hot pressing and adjusting the mass ratio of SPI to composite nanofibers at the same time.The morphology,mechanical properties and thermal properties of the composite membrane were studied and characterized.The results show that PI/GO composite nanofibers significantly improve the mechanical properties of SPI composite films,the highest tensile strength and modulus are 443.15±11.25MPa and 4.95±0.48GPa,which are 598.5%and568.9%higher than neat SPI film,respectively.With the increase of aligned electrospun PI/GO composite nanofibers content,the thermal performance of the composite films are gradually improved.The T5%from 460.5°C to 485.7°C,the increase was 25.2°C;the T_10%from 496.8°C to 520.1°C,the increase was 23.3°C;the residual rate at 800°C increased from 44.1%to 53.6%.